The present invention relates to an engine starter.
There exists an engine starter that includes a motor unit; a drive shaft that rotates by being subjected to a driving force of the motor unit; a pinion gear that spline-fits to the drive shaft; and an electromagnetic controller that connects the motor unit with a battery and allows the pinion gear to be engaged with a ring gear at an engine side by displacing the pinion gear toward a tip end side (see, for example, Japanese Published Unexamined Patent Application No. 2007-71043). The motor shaft of the motor unit and the drive shaft are disposed concentrically such that the engine starter is radially downsized. In this configuration, the electromagnetic controller can include an exciting coil unit. The exciting coil unit is disposed on an inner peripheral surface of a cylindrical case body for covering the pinion gear. The exciting coil unit includes a coil main body; and an exciting piece that is positioned at a tip end side of the coil main body so as to be magnetized according to an excitation of the coil main body. The electromagnetic controller can also include a plunger that is disposed so as be movable in an axial center direction in a ring-shaped space that is formed on an inner diameter side of the exciting coil unit. The plunger carries out operations for connecting the motor unit with the battery and pushing the pinion gear out when the plunger is displaced from an non-acting position to an acting position under an attracting force based on magnetization of the exciting piece. However, there exists a problem in that a plunger displacement stroke needs to correspond with a longer operation stroke because operation strokes of each of the operations are different.
In order to solve the problem, the plunger is provided with a first plunger on an outer diameter side and a second plunger on the inner diameter side. The first and second plungers are layered radially on the drive shaft and movable relative to each other in the axial center direction. The first and second plungers are also displaceable individually by excitation of the exciting piece. As a result, displacement of the first plunger to an acting position from a non-acting position causes the motor unit to be conductive to the battery, whereas displacement of the second plunger to an acting position from a non-acting position causes the pinion gear to be pushed out. Thus, each of the operation strokes is suitable for their own operations.